In the case where a shape steel with an H-shape or a groove shape or sheet metal is bent into an L shape or an angular U shape, and then such bent members are assembled to manufacture a frame structure, generally, these members are joined by welding. Upon this welding, in order to accurately adjust the positions of the members and improve the work efficiency of the welding, a special fixture and an exclusive welding technician are needed. In addition, in the case of performing such welding, since thermal distortion due to welding occurs, repair work such as distortion removal is needed. Thus, a problem of causing much labor and cost arises.
In order to solve this problem, an insertion frame structure is proposed which is composed of a pair of primary members with an angular U shape and a plurality of auxiliary members joined with the primary members by inserting both end portions of the auxiliary members to the primary members. In this insertion frame structure, latch holes with a rectangular shape are formed on the primary members, convex portions to be engaged with the rectangular-shaped latch holes are provided at the end portions of the auxiliary members, the convex portions are engaged with the rectangular-shaped latch holes, and these members are swaged with a latch member such as a rivet, thereby joining these members (for example, see Patent Document 1).